CN109216632B - A kind of preparation method of porous polyvinyl alcohol battery separator - Google Patents

Abstract

The invention discloses a preparation method of a porous polyvinyl alcohol battery separator, which is to obtain a high-porosity polyvinyl alcohol separator by suppressing the hydrogen bond between the hydroxyl groups of polyvinyl alcohol by a low temperature method. The method of the invention successfully solves the problem that the pore size of the polyvinyl alcohol separator decreases or disappears completely due to the hydrogen bond effect during the preparation process, and the prepared high-porosity polyvinyl alcohol separator has larger pore size and better electrolyte compatibility. sex.

Description

A kind of preparation method of porous polyvinyl alcohol battery separator

technical field

The invention relates to a preparation method of a polymer diaphragm in the field of new energy batteries, in particular to a preparation method of a high-porosity polyvinyl alcohol diaphragm obtained by suppressing the hydrogen bond between the hydroxyl groups of polyvinyl alcohol by a low temperature method.

Background technique

As a biodegradable polymer material, polyvinyl alcohol can be mass-produced by non-petroleum routes. It is inexpensive, and has the characteristics of oil resistance, solvent resistance and good mechanical properties. It has a wide range of applications in medicine and food. Due to the ductility and high mechanical properties of polyvinyl alcohol, it is often used to prepare thin-film products, and it is expected to be used in the field of new energy batteries: as a battery separator. Polymer separators with high performance, environmental protection, low toxicity and safety are the current research hotspots in the field of battery separators.

PVA battery separators are rarely reported so far. In 2015, WeiXiao used a non-solvent phase separation method to prepare porous polyvinyl alcohol separators and applied them in lithium batteries. However, the electrolytes of the polyvinyl alcohol separator obtained by this method of drying at room temperature have limited compatibility and pore size, which is caused by the hydrogen bonding between the long chains of polyvinyl alcohol. During the drying process at room temperature, with the continuous volatilization of the non-solvent phase ethanol, the structure of the polyvinyl alcohol separator will shrink due to the mutual attraction of hydrogen bonds. The low porosity caused by this phenomenon will degrade the electrochemical performance of lithium batteries. At present, how to solve the problem of pore size shrinkage caused by hydrogen bonding in the preparation process of polyvinyl alcohol separator has not been reported yet. Therefore, it is urgent to explore a simple and effective method to inhibit the hydrogen bonding in the preparation of PVA separators.

SUMMARY OF THE INVENTION

In order to avoid the technical problems existing in the above-mentioned prior art, the present invention provides a preparation method of a porous polyvinyl alcohol battery separator, which utilizes a low temperature method to inhibit the hydrogen bonding between polyvinyl alcohol hydroxyl groups to obtain a high porosity polyvinyl alcohol separator.

The preparation method of the porous polyvinyl alcohol battery separator of the present invention comprises the following steps:

Step 1: Add polyvinyl alcohol solid particles and water into the reactor, and keep stirring at 80-130 ° C until the polyvinyl alcohol solid particles are completely dissolved, and form a colorless and transparent solution, which is cooled to room temperature for use;

Step 2: uniformly coat the polyvinyl alcohol solution obtained in step 1 on a glass flat plate by a film coating device to form a film of a certain thickness, and immerse it into the non-solvent phase liquid at a constant speed, and let it stand for 3-24 hours;

Step 3: The film is taken out from the non-solvent phase liquid and peeled off from the glass plate, placed in a container and kept flat, and then kept at 0°C to -90°C for 0.2h-6h, and finally a high-porosity polyvinyl alcohol membrane is obtained .

In step 1, the alcoholysis degree of the polyvinyl alcohol solid particles is 70%-99%.

The mass concentration of the polyvinyl alcohol solution obtained in step 1 is 1-15 wt %.

In step 2, the thickness of the film is regulated by a film coating device, and the thickness is 8 μm-500 μm.

In step 2, the non-solvent phase liquid is methanol or ethanol.

In step 3, during the process of keeping the film at 0°C to -90°C for 0.2h-6h, the internal pressure of the container is reduced to 0.1Pa-10 ⁵ Pa.

In step 3, the temperature at which the film is placed in the container is preferably lower than -30°C.

Compared with the prior art, the advantages of the present invention are:

1. The low-temperature method of the present invention prepares a high-porosity polyvinyl alcohol diaphragm, which is low in cost, easy to operate, and has the possibility of industrialization.

2. The method of the present invention successfully solves the problem that the pore size of the polyvinyl alcohol membrane decreases or disappears completely due to the hydrogen bond effect during the preparation process.

3. The high-porosity polyvinyl alcohol separator prepared by the method of the present invention has larger pore size and better electrolyte compatibility.

Description of drawings

Figure 1 is a digital photo of the high-porosity polyvinyl alcohol separator prepared by the low-temperature method in Example 1.

FIG. 2 is a scanning electron microscope image of the cross-section of the polyvinyl alcohol separator prepared under the conditions of 25° C. and -60° C. in Example 1. FIG.

FIG. 3 is the contact angle test of the surface of the high-porosity polyethylene separator prepared by the low-temperature method of the commercial electrolyte in Example 1. FIG.

Detailed ways

The technical solutions of the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

Example 1:

1. Add 10g of polyvinyl alcohol solid particles (model: 1799, alcoholysis degree of 99%) and 90g of water into the single-neck flask equipped with the magnet, and continue magnetic stirring at 90 ° C until the polyvinyl alcohol solid particles are completely dissolved, And form a colorless and transparent solution of 10wt% polyvinyl alcohol, which is cooled to room temperature for use;

2. Pass the obtained polyvinyl alcohol aqueous solution through a film coating device to form a film with a thickness of 50 μm on a glass plate, immerse it in absolute ethanol at a constant speed, and let it stand for 12 hours; take out the film from the ethanol and remove it from the glass plate It was peeled off and placed in a container at -60°C, kept flat, and the internal pressure was reduced to 1 Pa for 4 hours, and finally a high-porosity polyvinyl alcohol separator was obtained.

3. A comparative test is added here, the film taken out from ethanol is peeled off from the glass plate and placed at normal temperature (25° C.) to volatilize to obtain a polyvinyl alcohol film.

Figure 1 is a digital photo of the high-porosity polyvinyl alcohol separator prepared by the low-temperature method in Example 1. As can be seen in the figure, the high-porosity PVA separator appears white and has a smooth surface.

FIG. 2 is a scanning electron microscope image of the cross-section of the polyvinyl alcohol separator prepared under the conditions of 25° C. and -60° C. in Example 1. FIG. It can be seen from the figure that almost no holes are observed in the section of the polyvinyl alcohol film prepared at room temperature (25 °C), while the section of the polyvinyl alcohol film prepared at -60 °C is full of holes, and the hole diameter is about 0.5 -1.5μm. This shows that the high-porosity separator can be obtained by overcoming the hydrogen bonds between the long chains of polyvinyl alcohol by the low-temperature method, which proves the success of the experiment.

FIG. 3 is the contact angle test of the surface of the high-porosity polyethylene separator prepared by the low-temperature method of the commercial electrolyte in Example 1. FIG. The electrolyte used is commonly used 1M LiPF ₆ /EC:DMC 1:1v/v. It can be seen from the figure that the contact angle between the electrolyte and the polyvinyl alcohol separator prepared by the low temperature method is only about 3.0°, which reflects the strong electrolyte compatibility.

Example 2:

1. Add 15g of polyvinyl alcohol solid particles and 85g of water to the single-necked flask equipped with the magnet, and continue magnetic stirring at 110 ° C until the polyvinyl alcohol solid particles are completely dissolved, and form a colorless and transparent solution of 15wt% polyvinyl alcohol, Cool to room temperature for later use;

2. Pass the obtained polyvinyl alcohol aqueous solution through a film coating device to form a film with a thickness of 30 μm on a glass plate, immerse it in absolute ethanol at a constant speed, and let it stand for 12 hours; take out the film from the ethanol and remove it from the glass plate It was peeled off and placed in a container at -80°C, kept flat, and the internal pressure was reduced to 1Pa for 4h, and finally a high-porosity polyvinyl alcohol separator was obtained.

Example 3:

1. Add 5g of polyvinyl alcohol solid particles and 95g of water to the single-necked flask equipped with the magnet, and continue magnetic stirring at 110 ° C until the polyvinyl alcohol solid particles are completely dissolved, and form a 5wt% polyvinyl alcohol colorless and transparent solution, Cool to room temperature for later use;

2. Pass the obtained polyvinyl alcohol aqueous solution through a film coating device to form a film with a thickness of 30 μm on a glass plate, immerse it in anhydrous methanol at a constant speed, and let it stand for 6 hours; take out the film from the methanol and remove it from the glass plate. It was peeled off and placed in a container at -30°C, kept flat, and the internal pressure was reduced to 1Pa for 6h, and finally a high-porosity polyvinyl alcohol separator was obtained.

Example 4:

1. Add 2g of polyvinyl alcohol solid particles and 98g of water to the single-necked flask equipped with the magnet, and continue magnetic stirring at 100 ° C until the polyvinyl alcohol solid particles are completely dissolved, and form a colorless and transparent solution of 2wt% polyvinyl alcohol, Cool to room temperature for later use;

2. Pass the obtained polyvinyl alcohol aqueous solution through a film coating device to form a thin film with a thickness of 200 μm on a glass plate, immerse it in anhydrous methanol at a constant speed, and let it stand for 6 hours; take out the film from the methanol and remove it from the glass plate It was peeled off and placed in a container at 0°C, kept flat, and the internal pressure was reduced to 1 Pa for 12 hours, and finally a high-porosity polyvinyl alcohol separator was obtained.

Example 5:

1. Add 2g polyvinyl alcohol solid particles (model: 1788, alcoholysis degree is 88%) and 98g water into the single-neck flask equipped with the magnet, and continue magnetic stirring at 100 ° C until the polyvinyl alcohol solid particles are completely dissolved, And form 2wt% polyvinyl alcohol colorless and transparent solution, cooled to room temperature for use;

2. Pass the obtained polyvinyl alcohol aqueous solution through a film coating device to form a film with a thickness of 400 μm on a glass flat plate, immerse it in absolute ethanol at a constant speed, and let it stand for 12 hours; take out the film from the ethanol and remove it from the glass flat plate It was peeled off and placed in a container at -50°C, kept flat, and the internal pressure was reduced to 1Pa for 12h, and finally a high-porosity polyvinyl alcohol separator was obtained.

Claims (5)

1. A preparation method of a porous polyvinyl alcohol battery diaphragm is characterized by comprising the following steps: the method for inhibiting the hydrogen bond effect between polyvinyl alcohol hydroxyl groups by using a low-temperature method to obtain the high-porosity polyvinyl alcohol diaphragm comprises the following steps:

step 1: adding polyvinyl alcohol solid particles and water into a reactor, continuously stirring at 80-130 ℃ until the polyvinyl alcohol solid particles are completely dissolved to form a colorless transparent solution, and cooling to room temperature for later use;

step 2: uniformly coating the polyvinyl alcohol solution obtained in the step (1) on a glass plate by using a coating device to form a film with a certain thickness, immersing the film into a non-solvent phase liquid at a constant speed, and standing for 3-24 hours;

and step 3: taking the film out of the non-solvent phase liquid, peeling off the film from the glass flat plate, placing the film in a container, keeping the film flat, and keeping the film at 0-90 ℃ for 4-6 hours to finally obtain the high-porosity polyvinyl alcohol diaphragm;

in the step 2, the non-solvent phase liquid is methanol or ethanol;

in the step 3, the internal pressure of the container is reduced to 1Pa in the process that the film is kept at the temperature of between 0 and 90 ℃ for 4 to 6 hours.

2. The method of claim 1, wherein:

in the step 1, the alcoholysis degree of the polyvinyl alcohol solid particles is 70-99%.

3. The method of claim 1, wherein:

the mass concentration of the polyvinyl alcohol solution obtained in the step 1 is 1-15 wt%.

4. The method of claim 1, wherein:

in the step 2, the thickness of the film is regulated and controlled by a coating device, and the thickness is 8-500 μm.

5. The method of claim 1, wherein:

in step 3, the film is placed in a container at a temperature of less than-30 ℃.

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